1. Field of the Invention
The present invention relates to a biochip reader for measuring a plurality of types of biopolymers on a substrate, and in particular, relates to an improvement for enabling the measurement of a wider area on a substrate while maintaining a large numerical aperture.
2. Description of the Prior Art
There is well-known equipment which detects and analyze DNA or protein by labeling biopolymers such as DNA or protein with fluorescent materials, exciting those fluorescent materials through irradiation of the biopolymers with laser, and reading the fluorescence generated from the fluorescent materials. In this case, biochips on which DNA or protein or the like labeled with fluorescent materials is spotted in an array are utilized.
FIG. 1 is a conceptual configuration drawing showing an example of conventional incident-light fluorescence biochip readers mentioned in the gazette of Japanese Laid-open Patent Application No. 2000-207007. This biochip reader reads hybridization of unknown gene α as shown in FIG. 1(b) and biochip 6 composed of a plurality of DNA molecules (genes) A, B, C, . . . whose sequences are known bonded on substrate PL as shown in FIG. 1(a) using a mechanism as shown in FIG. 1(c).
In FIG. 1(c), light from light source 1 (laser) becomes the parallel light at lens 2 and, after transmitting dichroic mirror 4, is focused on biochip (or called a sample) 6 by means of lens 3. The light returned from biochip 6 becomes parallel again by means of lens 3 and is reflected with dichroic mirror 4 and forms an image on camera 9 by means of lens 8.
In this case, the surface of biochip 6 is scanned by moving the stage (not shown in the drawing) on which biochip 6 is mounted in the directions of X and Y using a driving means (not shown in the drawing) to obtain the image of the surface of biochip 6.
However, there are the following problems with such conventional systems:
(1) FIG. 2 is a drawing for the optical system shown in FIG. 1. The measurable range is determined by the CCD camera used and magnifications of lenses 3 and 8 and the following relations exist between them:a1/a2=f1/f2=NA2/NA1                where a1 is the width of measurement area (field of view of camera 9) of biochip 6.                    a2 is the width of the detecting element surface of camera 9.            f1 is the focal length of lens 3.            f2 is the focal length of lens 8.            NA1 is the numerical aperture of lens 3.            NA2 is the numerical aperture of lens 8.                        
Due to these relations, if measurement area a1 is widened, the image becomes dark because the incident NA1 becomes small.
(2) When the size of the detecting element, CCD, of camera 9 is, for example, ½ inch, its field of view is about 4.8×6.4 mm2. This value is about {fraction (1/60)} smaller than the measurement area of 75×25 mm2 in the case where sample 6 is, for example, a slide glass. Furthermore, in the case of the system where conventional one-beam laser irradiates a sample which is moved with a stage, and the total light quantity for each step is detected with photomultipliers or the like, a precision stage is required and so the system is expensive and measurement is time-consuming. If it is assumed that measurement is made in about 10-μm step using one-beam exciting light, a measurement area of 75×25 mm2 must be measured by moving the stage 1.875×107 times.